tifauczWhile development of Carbon we have decided that it is going to be row 4. In the initial design it was row 3. If you are interested in how Carbon evolved see the following IC Carbon Thread on GeekHack:
https://geekhack.org/index.php?topic=72241.0
In my opinon Planck should be 1-2-3-4, but as you can see these kits reflect not only my opinion but opinions from many other people, who were active in developing Carbon. So there is Development phase where we do brainstorming and changes to specific kits. And there is GB phase (right now), which is actually the deadline for changing kits. The only things we can add are spacebars in available sizes. Currently all the possible spacebar sizes are already available for purchase.